(with-eval-after-load 'company
  (define-key company-active-map (kbd "M-n") nil)
  (define-key company-active-map (kbd "M-p") nil)
  (define-key company-active-map (kbd "C-n") #'company-select-next)
  (define-key company-active-map (kbd "C-p") #'company-select-previous))

Company is a text completion framework for Emacs. The name stands for "complete anything". It uses pluggable back-ends and front-ends to retrieve and display completion candidates.